This invention relates to a design for a two-stroke engine that reduces the exhaust pollutants and that improves the delivery ratio characteristics at a wide range of engine speeds. The delivery ratio is defined as the ratio of mass of delivered charge to displaced volume times the ambient density. Two-stroke engines are known for their simplicity and high specific output. However, they have drawbacks of poor emissions and efficiency characteristics. It is estimated that fuel consumption emissions of two-stroke engines are 1.5 to 2.0 times that of equivalent four-stroke engines and hydrocarbon emissions of two-stroke engines are 10-20 times that of equivalent four-stroke engines respectively. Some small utility engines produce up to 50 times the pollution of trucks on a per horsepower per hour basis. High unburned hydrocarbon emissions arise because in a carburetted two-stroke engine the scavenging process is carried out by a fresh mixture of air and fuel. Some of the air-fuel mixture mixes with the residual exhaust gas as it scavenges the cylinder and a small fraction of the charge is lost due to short circuiting. The net effect is that 25-40% of the charge may be wasted resulting in high fuel consumption and high levels of unburned hydrocarbons. It is believed that the fraction of the exhaust gas leaving the cylinder at a particular time is rich in unburned hydrocarbons. Investigations relating to delivery ratio and engine speed have shown that delivery ratio is dependent on engine speed for a given inlet port timing and for optimum delivery ratio inlet port timing is different for different speeds. It is the objective of this invention to recirculate that fraction of the exhaust gas rich in unburned hydrocarbons to minimize the pollutants and also improve the efficiency of the engine by way of trapping and recirculating the short circuited fresh charge and improve the delivery ratio over a wide range of speeds.